The 2 new patterns added to the User group use the RGB level that are settable in the first 3 patterns.

The custom sizing allows setting the window size in .1% steps.

The custom size + APL pattern allows setting both the window size and an APL.

As you vary the size of the window the background level is adjusted to give the desired APL.

If it can't meet the requested APL, a greater-than or less-than sign is displayed next to APL to indicate this (.ie setting RGB=240,240,240, the custom size to 90.0% and the APL to 30% would give the greater-than sign next to APL).

Added rs232 access to the new patterns.

The rs232 format for the new User size pattern is "ZY7TsSSSRRRGGGBBB" with SSS being 3 digits (000-999) for 0-99.9% area of screen.

The rs232 format for the user defined size + APL pattern is "ZY7TsSSSAAARRRGGGBBB" with AAA being 3 digits to be set to 000-100 for 0-100% APL.

Fixes audio issues seen that could give noise or no audio with some equipment.

Added a shorter option for audio mute length under Input: Audio Setup: Mute Control. The default is mute length is "Long" but options include Short, Medium, and Long. Previously, the options were only Short and Long which have now become the Medium and Long values.

Fixed up an older bug (recently made worse in 112513) which depending on equipment and settings could intermittently (or regularly) result in delaying turn-on of video output. Could be double normal output turn-on time and feasibly even longer.

Bugfix for issue created in 112513 release causing an output to not turn on if only one output is connected.

I thought I'd post this here since it's relevant to LS users. I ran the Argyll lutted eeColor through the LS quickprofile routine and noticed it appears that the gamma is being calculated incorrectly for the Rec709 and ITU-R.BT1886 labeled "Color Standard Target". The gamma for Rec709 is an encoding gamma as is not typically used for target calibration but in any case it looks very different than a pure power law 2.2 curve, which is what LS is generating in it's gamma tab. Likewise the ITU-R.BT1886 selection is generating what looks like a pure power law 2.4 curve and this will only be correct in the case where the display black is identically zero. At the very least the user should be informed that the program is making these modifications to published standards so there will be no confusion. For the BT.1886 calculation I would recommend using the measured black and white level and calculating the correct quantity.

The blue curves are what a proper BT.1886 gamma should look like for my display black level.

I discussed this very point with Steve and his calibration expert at length about 6 months ago and they were both adamant that black compensation wasn't part of the BT1886 specs and that a power 2.4 gamma was the correct way to do this. I asked what's the difference between selecting BT1886 and selecting rec709+2.4 power gamma then? And they said: none.

Maybe they will listen if more users raise this issue and complain about it. At the time I did, no one seemed unhappy about this so I gave up as it didn't feel like something they were interested in implementing properly (or let's say differently).

After all, I wasn't a user, I was just evaluating the software, but having to debate about something as obvious as this was a bit unexpected.

I discussed this very point with Steve and his calibration expert at length about 6 months ago and they were both adamant that black compensation wasn't part of the BT1886 specs and that a power 2.4 gamma was the correct way to do this. I asked what's the difference between selecting BT1886 and selecting rec709+2.4 power gamma then? And they said: none.

Maybe they will listen if more users raise this issue and complain about it. At the time I did, no one seemed unhappy about this so I gave up as it didn't feel like something they were interested in implementing properly (or let's say differently).

After all, I wasn't a user, I was just evaluating the software, but having to debate about something as obvious as this was a bit unexpected.

That's a serious misreading of the recommendation which no "calibration expert" would ever make. There are two formulas recommended, the first is the one that should be used while the second is for legacy raw CRT transfer function emulation. The first formula (that HCFR, CM, CP, Argyll etc. all use) will only approach a pure power law with exponent of 2.4 in the limit of zero black level.

That's a serious misreading of the recommendation which no "calibration expert" would ever make. There are two formulas recommended, the first is the one that should be used while the second is for legacy raw CRT transfer function emulation. The first formula (that HCFR, CM, CP, Argyll etc. all use) will only approach a pure power law with exponent of 2.4 in the limit of zero black level.

If you target a pure power law of 2.4 using a display with a black level of 0.05 cd/m^2 for example you will clip dark levels below about 4% input video level. BT.1886 will tailor the transfer function to preserve that dark detail.

BT1886 is an idea to match modern flat panel displays to older CRTs - it is not a recommendation that has been adopted widely at all, and will probably (and should?) just disappear...
When most displays in the world are flat panels why attempt to make them emulate old CRT technology?

The BT1886 standard defines the transfer characteristics of a display - the electro optical transfer function - and defines this using a function which is simply a gamma 2.4 function between black (minimum light) and white (maximum light). There is no change in the blacks in the standard.

In the document there is an annex recommendation (so not part of the standard) that modifies the standard function to have a lower gamma in the blacks. This is the bit for simulating legacy CRTs...

All in all, BT1886 is best ignored, other than if we can all agree on a standard gamma, as that is missing for the Rec709 standard.

But in today's world most material is mastered at 2.2 gamma, as that is the gamma of the old Sony Grade 1 CRT displays.

Sorry that is just not correct - no clipping will never occur with correctly calibrated displays.

Steve

Steve, if the display's on/off isn't at least 40000:1, it will clip blacks with a power 2.4 gamma. This is precisely why BT1886 is so helpful, as it allows you to target a higher gamma for most of the curve, except where blacks would clip if the on/off of the display doesn't allow you to target a power 2.4 curve. Before BT1886, we used to do this manually, with custom targets for the lower levels, to allow the signal to come out of black faster. This has nothing to do with CRTs. It's still an issue with most modern displays. LCOS, SXRD, DLP, etc. With a power gamma, the option is to target a 2.3 or 2.22 gamma instead, which isn't ideal in a bat cave / dedicated room.

I don't know where you get the numbers about 2.2 being the most used. The last poll I saw showed no clear standard for gamma, and about as many people calibrating for 2.22 as 2.4 as BT1886 (in post-prod houses/studios). I thought the standard was becoming BT1886, now the question is does that mean rec 709 + 2.4 power as you say or what we (Zoyd, myself, and most other calibration software) call BT 1886, which does include black compensation.

We've already discussed this so I'm sure I won't change you're mind. What I don't understand is why none of your users are complaining about this.

I'm sorry, but that's just not correct - with a correctly calibrated display clipping will never occur - ever.
I have no idea where you get that idea from?
The on/off black level of a display has no relevance to accurate calibration.

If you want to alter lower gamma for your own idea of what an image should look like in the shadows, that's up to you. but that has no relevance with regard to accurate calibration.

The calibration of a display is aimed at match the intended look of the production company (the Dop and Colourist) and I can promise you they do not grade on displays with randomly altered shadow levels.

The annex in BT1886 is just intended to match legacy CRT displays, with a hint at legacy Brightness/Contrast.

The BT1886 standard defines the transfer characteristics of a display - the electro optical transfer function - and defines this using a function which is simply a gamma 2.4 function between black (minimum light) and white (maximum light). There is no change in the blacks in the standard.

Question away...
The annex is NOT part of the specification - as I have repeatedly stated.

And further, as there is no mastering being done to the details of the annex, there is no material that expects to be viewed under such display set-up conditions.
Is that not what calibration is all about - to match the conditions under which the original grading was performed?

As I say, if you want to alter the shadow details for your own viewing desires, that's fine, but that is not calibration.

I'm sorry, but that's just not correct - with a correctly calibrated display clipping will never occur - ever.
I have no idea where you get that idea from?
The on/off black level of a display has no relevance to accurate calibration.

If you want to alter lower gamma for your own idea of what an image should look like in the shadows, that's up to you. but that has no relevance with regard to accurate calibration.

The calibration of a display is aimed at match the intended look of the production company (the Dop and Colourist) and I can promise you they do not grade on displays with randomly altered shadow levels.

The annex in BT1886 is just intended to match legacy CRT displays, with a hint at legacy Brightness/Contrast.

The day production companies, DOP and colorists will all use the same gamma curve, I'll be happy to use that. As you said yourself, there is no standard as far as gamma is concerned. A few years ago, most blurays were mastered in SMPTE-C instead of rec-709 because post-prod companies were still using old CRTs.

So the question is not how can we follow a standard which doesn't exist yet, but rather which gamma curve represents the best compromise until such a standard exists for gamma.

In a dedicated room, BT1886 (with black compensation) is the best compromise in most cases when your display is unable to handle a 2.4 power curve due to the lack of on/off contrast.

Anyway, if none of your users complain about your implementation of BT1886, you are right to stick to your guns

BT1886 is an idea to match modern flat panel displays to older CRTs - it is not a recommendation that has been adopted widely at all, and will probably (and should?) just disappear...
When most displays in the world are flat panels why attempt to make them emulate old CRT technology?

If you want to impose your own personal interpretation of how the EOTF of "displays used in HDTV production and programme interchange" is calibrated you should inform your users of what you are doing and why, so that they can evaluate whether this is something they desire or not. Also, Change the label BT.1886 because it is incorrect.

This is not really a matter of opinion. This is relatively simple math. Assume a black level of 0.05 and a white level of 100. That's a contrast ratio of 2000:1. Also a assume a power law gamma of 2.4.

At 4% video the output will be 0.044, lower than the black level, pretty much the textbook definition of clipping.

(4%^2.4 = 0.044% and 0.044% * 100 = 0.044)

Even a 10,000:1 contrast display clips at 2% video when using a straight 2.4 power law.

The more interesting question is whether it is better to use a straight 2.4 power law on very high contrast displays that could presumably accept this without clipping or use BT.1886? It makes a difference. At 5% video on a 100 cd/m2 40,000:1 display a 2.4 gamma will result in 0.075 output. BT.1886 recommends 0.124, which is not a trivial difference.

To my eyes the BT.1886 recommendation is clearly better, but that's a subjective response.

Ah - have you not noticed there is no 'user black level' or 'black target level' that can be set in LightSpace?
That is why a correctly calibrated display can never clip...
The value of black is always the min the display can achieve.
There really is no other way to accurately calibrate different displays so they display image detail identically based on their relative black levels.

As many witll understand, this is not as easy as it sounds as few probes can accurately read the real black value.
But, there are ways to manage this, which is a key part of the 'colour engine' built into LightSPpace.

Not understanding this is a fundamental error in may calibration systems.

And as for imposing our own interpretations of BT1886, that's just incorrect.
We only work to the actual standards - not some random concept of what's intended, and thsi included not using annex data that is not part of the standard.

Oh - and an annex is just that - an annex, not part of the main content of the document.
In this case it is not part of the specification, and attempting to match legacy CRT displays is just not valid as even in post-production companies they no longer exist...

Steve, the reason why we had this discussion when I evaluated Lightspace is because the LUT produced by the software was clipping blacks on my display with a 2.4 power gamma curve, even when choosing BT1886.
If the software has improved since, I'd be happy to give it another try, but that theory, at least at the time, didn't work on my display (a JVC rs-45 with an on/off of at most 40000:1 in my setup).
With other calibration software, I can use BT1886 and the blacks do not clip. Before BT1886, I would use a 2.4 power curve and slightly adapt the first levels in order not to crush blacks.
With LS, I would clip blacks even with BT1886 (which makes sense given the way you have implemented it).
The only option I have with LS is to target a lower power gamma curve like 2.35 or 2.3 which isn't what I want to do.
This is not a dig at LS by the way, your software has great advantages and quite a few downsides, like all others.
It's just that not handling BT1886 in a way that helped preventing the clipping of blacks made it much less useful in my setup.
What I don't understand is why you don't give at least the option of using BT1886 with the annex.
What would you lose exactly in offering a "strict" BT1886 and a BT1886 with annex options?

And as for imposing our own interpretations of BT1886, that's just incorrect.
We only work to the actual standards - not some random concept of what's intended, and thsi included not using annex data that is not part of the standard.

Steve

Quote:

Oh - and an annex is just that - an annex, not part of the main content of the document.

Not sure why you are hung up on the word annex. I'll ask again - what standard and what document are you referring to that recommends a pure power law 2.4 EOTF?

The simple fact is that BT.1886 is the ITU recommended EOTF and it incorporates display black level. For you to substitute a pure power law with exponent of 2.4 and call it BT.1886 is a misrepresentation.

I find the pain from banging my head against the same wall goes away when I stop...

Fine, since there is nothing you can say that justifies your substitution of a pure power law EOTF with exponent of 2.4 in lieu of the using the correct BT.1886 formula, I will take that as tacit admission that the current implementation of the target space labeled ITU-R-BT.1886 in LightSpace is broken.

Simple fact - the implementation of BT1886 in LightSpace is totally correct as per the specification.
And further, is exactly as is implemented in the professional world (where it is used - which is few and far between...)

Since Steve is unwilling to provide even a simple reference to support his statement I will just show for other readers how this is can be a serious and misleading situation.

Suppose an inexperienced user who has used one of the available software packages that correctly implements BT.1886 to calibrate his display decides to demo LS. He runs the quickprofiler and sees his RGB separation values look pretty good.

He then displays the dE tab:

Damn, CM tells me all my dEs are well below 2, what's going on?

Whereas if he had chosen (again incorrectly labeled rec709) he would have seen this:

Not perfect, but much closer to expectations because the rec709 selection is using an EOTF closer to the proper implementation of BT.1886 on this display.

Now an inexperienced user might not realize that the program is at fault here and not his prior calibration. In my opinion this is an unethical situation to propagate.